Case of the missing coolant

[Jim Ragain]

My Rotax 912 ULS (2011 CTLS) is losing coolant, but it is not leaking out on the floor and none shows up on the inside of the cowling or on the firewall.  ???  I have refilled the reservoir twice in the past month (approximately 20 hours of flying).

[Tommy Mc]

Hi Jim.  There was a case recently here in Ireland. A Tecknam arrived in a Field in Waterford with Engine failure.  The hose clamp on Number 3 was not clamped all the way up onto metal and was leaking un-noticed.  The Hose did nor blow off in flight as the filler cap was not holding pressure resulting in the coolant expanding out to the bottle during flight and the next Pilot topping it up eventually There was enough of a leak to be pulled into the Carb...........   

http://www.aaiu.ie/sites/default/files/report-attachments/REPORT 2020-005_0.pdf

Best to read the report..... maybe its your Filler Cap...... I'm not a mechanic.....

T

[Roger Lee]

It's either  water under a hose clamp. Move compression clamps up to, but not over the metal flared fitting underneath. This adds extra pressure at that point and it won't leak. The other spot is where the 90 degree fitting screws into the flange on the top of each cylinder. Either way the airflow through the engine blows these off and drys them up. After landing stay around a while and pop the top cowl off and watch closely.

The other places are the two 17mm hoses under each cylinder. Make sure these clamps are up to the metal flare underneath, but not on top or past it.

[Jim Ragain]

Thanks Roger and Tommy.